Brewers Friend pitch rate starter calculator question

[sky4meplease]

I notice quite a large difference in growth rates between Braukaiser-Sirtplate and C. White-Stir Plate when doing my calculations on Brewers Friend.
If they were close I wouldn't sweat it but it does seem substantial.
Help anyone?

 

[sky4meplease]

If I do a 2L starter from a Liquid Pack/Vial that is 58% viable the difference in Ending Cell Count (between Braukaiser's stir plate model and C. White's stir plate model) is 133 Billion cells. Those two numbers aren't even in the same ball park.
I have been using Braukaiser's stir plate model and my gut feeling is I have been under pitching. Especially my lagers. Way under pitching my lagers.
Maybe someone can put my mind at ease but I am trying to figure out how both of these models can be in the same calculator unless they are both on the conservative side.

 

[WoodlandBrew]

I trust Kai's equation.

It is based on cell counts of actual starters done on stir plates and his results were duplicated and confirmed by others.

The Chris White equation is based on starters that were not aerated and not stirred and then a "correction factor" was applied based on anecdotal evidence.

 

[sky4meplease]

Thanks for replying.
I was really surprised to see the difference between the two methods.
The largest difference I saw was with single step starters.
The more steps with larger cell numbers seemed to bring the two closer together.
I see some cell counting in my future.

 

[WoodlandBrew]

Here is the microscope i use:
http://www.woodlandbrew.com/2012/11/amscope-binocular-compound-microscope.html

 

[sky4meplease]

Thanks again Woodlandbrew. Your quick responses and reliable information are a valuable resource.
I started picking up the bits and pieces I will need for this new adventure in brewing science while I continue to wrap my head around the processes and further my knowledge.
I found your microscope on eBay for $190.00 but may take advantage of access I have to one at the waist water treatment facility here in town while I continue getting everything else in order and hang on to hope I may find a little better price on my own.

 

[WoodlandBrew]

You're welcome. Feel free to send me a PM or email if you have any questions. For viability and cell density of yeast 400x is all you really need. The 1000x oil immersion is nice on occasion, but I hardly ever use it. I would be a little leery of buying a used microscope without looking through it first. The optics are the most important thing in a scope, and a little scratch can make a big difference. That being said, I've heard several people say they are very happy with microscopes that they got on Ebay. I'm very happy with my Amscope. Celesteon is also good for the price. If you can find an Olympus or Baush & Lomb in good condition that would be an excellent scope.